Instability in charged Gauss-Bonnet-de Sitter black holes

TL;DR

This paper investigates the stability of charged Gauss-Bonnet-de Sitter black holes under gravito-electromagnetic perturbations, revealing gravitational instability in higher dimensions and analyzing the role of BF bound violations.

Contribution

It provides a comprehensive analysis of the instability criteria for charged Gauss-Bonnet-de Sitter black holes, including numerical and theoretical insights into the conditions for instability.

Findings

Instability occurs in five or more dimensions.

BF bound violation is sufficient but not necessary for instability.

Constructed the full parameter space for stability and instability.

Abstract

We study the instability of the charged Gauss-Bonnet de Sitter black holes under gravito-electromagnetic perturbations. We adopt two criteria to search for an instability of the scalar type perturbations, including the local instability criterion based on the $AdS_2$ Breitenl\"{o}hner-Freedman (BF) bound at extremality and the dynamical instability via quasinormal modes by full numerical analysis. We uncover the gravitational instability in five spacetime dimensions and above, and construct the complete parameter space in terms of the ratio of event and cosmological horizons and the Gauss-Bonnet coupling. We show that the BF bound violation is a sufficient but not necessary condition for the presence of dynamical instability. While the physical origin of the instability without the Gauss-Bonnet term has been argued to be from the $AdS_2$ BF bound violation, our analysis suggests that the BF bound violation can not account for all physical origin of the instability for the charged Gauss-Bonnet black holes.